Question

How can we write an algebraic expression to describe a two-digit number whose unit's digit is 5 less than the ten's digit?

(write a algebra equation, look at the image for example)

Answer 1

Answer:

Let x= the ones digit

Then x+5=the tens digit

 

Hence the equation is

 

10(x+5)+x=x+5+x+63

10x+50+x=2x+68

11x+50=2x+68

 -2x-50  -2x-50

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        9x=18  Divide both sides of the equation by 9

          x=2

 

Hence the number is 10(2+5)+2=10(7)+2=70+2=72.